From Edmund Scientifics:
"The handle turns the cam shaft and the eccentric shaped cams push the rods up. This shows how a circular turning motion can be converted into an up-and-down movement. The cams can be repositioned on the shaft to change the movement of the snake."
The kit comes complete with everything your need to build the automaton except a screwdriver to put it together. Here is a 16-Piece Precision Screwdriver Set with everything you might need for delicate projects.
Here's the product page for the Make A Snake Mechanical Wooden Automaton Kit.